“Indeed,” said Mr. Herne, “though I had not thought of that theory it seems to me so plausible, now that you mention it, that I think the officers will show rare acumen if they adopt it.  Very properly may they hold that some projectile might have been shot through the partly opened window and none of us have detected the act.”

“Ah, yes,” rejoined Maitland; “but when I ask them where this implement is under this assumption, and remind them of what I shall already have told them, viz., that Mr. Darrow sat back to the window as well as over eight feet from it, and sat in a chair, the solid back of which extended, like a protecting shield, fully six inches above the top of his head, they will find it difficult to show how, unless projectiles travel in sharp curves or angles, a man in this position could thus receive a wound directly beneath his chin, a wound so slight as not to penetrate the thyroid cartilage immediately under it.

“The abandonment of this hypothesis will force them to relinquish the idea that the murder was committed from without.  What then remains?  Only the second alternative.  They must either give up altogether the idea of murder, or have recourse to what is known as the theory of exclusive opportunity.”

“Theory of exclusive opportunity,” repeated Gwen, as a puzzled look overspread her countenance.  “I—­I fear I do not quite understand what you mean.”

“Pardon me, Miss Darrow, for not making my meaning clearer to you,” said Maitland with a deferential inclination of the head.  “The theory of exclusive opportunity, to state it plainly in this case, means simply this:  if Mr. Darrow were murdered, some one of us five, we being the only ones having an opportunity to do the deed, must be the assassin.  Whether this view be taken, or that of suicide, it becomes of paramount importance to find the weapon.  Do you not now see why I objected to having anyone leave the room?  If, as appears likely from my search, the weapon is not to be found, and if, as I feel reasonably certain, either the suicide or the murder theory be substantiated, then, anyone who left the room before official search was made would be held to have taken the weapon with him and disposed of it, because his would have been the exclusive opportunity of so doing.  Someone must have disposed of it, and no one else had a chance to do so; that would be the way it would be stated.  But, since no one of us has left the room, a thorough search both of it and of our persons, must convince the officers that we, at least, are not responsible for the fact that the weapon is not forthcoming.”

Maitland paused and looked at Browne as if he expected him to speak, but that gentleman only shut his square jaws the more firmly together and held his peace,—­at least in so far as words were concerned.  If looks, like actions, “speak louder than words,” this black visage with its two points of fire made eloquent discourse.  I charged all this display of malice to jealousy.  It is not altogether pleasant to be placed at a disadvantage before the one being whose good opinion one prizes above all things else,—­that is to say, I have read that such is the case.  I do not consider my own views upon such matters expert testimony.  In all affairs of the heart my opinions cease to have weight at exactly the point where that organ ceases to be a pump.